I went to start the Montero up this morning and the voltage gauge went up to 16 volts and then it dropped back down to 12 volts after a few minutes. Could not get the front lights to work so I went down to my favorite mechanic to have him tell me what was up. I noticed also my warning lights all lite up as well. He ran a electrical test and said my battery was bad and the rebuilt alternator was not working properly and that they both needed to be replaced as well. He told me that the problem with a rebuilt alternator is if the shop only replace the problem parts that there is a good chance another part will fail if the entire alternator is rebuilt.He said the warning lights will come on when the alternator is bad; is that true. Picked up a alternator and new battery from O'Riley today to maybe install this weekend. Does it make sense the warning lights come on when your charging system is bad or is this problem caused by something else ie like a fuse? <img src="/forums/images/graemlins/confused.gif" alt="" />

The described symptoms sound about like my experiences. That should fix it.

John B.

I know on most cars, a dummy light will come on when the voltage drops below a certain point. It doesn't normally point to a specific component, but the charging system in general. I would think that the scenario you describe is possible.

Sounds like the alternator to me, and I'd have to try just that and a charge until I saw that the battery was dead, not just discharged...